Optically enhanced defect reactions in semi-insulating bulk GaAs

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Abstract
We investigate in this paper a photomemory effect in the photocurrent of semi-insulating GaAs when it is illuminated with photons ranging from 1 to 1.35 eV. We observe a strong enhancement of the photocurrent after long excitation with those photons, which is thermally quenched between 123 and 135 K. We explain this phenomenon by a defect reaction, dealing with the association of two or more complex defects, as a result of the electrostatic interaction between the original defects when their charge state is changed by means of the illumination. The formation of this complex drives the sample into a high-sensitivity state, which we have called ‘‘on-state.’’ The dissociation of the photogenerated complex defect, due to thermal emission of electrons to the conduction band, restores the crystal into its normal photosensitivity state, which we have called ‘‘off-state.’’